In the United States and other milk-producing countries, milk is primarily used to manufacture cheese. However, only approximately half of the solids present in milk are coagulated and recovered as cheese; the remaining half are recovered as whey, a by-product of the cheese manufacturing process. Whey contains proteins, a milk sugar known as lactose, minerals and vitamins.
The treatment and disposal of whey frequently poses significant environmental problems. Whey is sometimes dried to be used as an extender in cattle feed, or in other processed food items such as candy bars. However, use in food applications is limited because of the high ash content of whey.
Using the more advanced technique of ultrafiltration, commercially valuable proteins can be recovered from whey. In ultrafiltration, pressure is applied to a solution to force whey through a semipermeable membrane. The openings of the membrane are sized to pass all portions of the whey except the proteins, which become concentrated. Whey proteins have long been used as food ingredients and in pharmaceutical applications.
The material which passes through the membrane is called whey permeate, also known as liquid permeate. Whey permeate contains lactose, minerals and vitamins. Lactose, used in baby food, bakery and pharmaceuticals, is commonly produced from whey permeate by evaporating and crystallizing it. Unfortunately, the recovery of lactose from whey permeate results in the byproduct delactosed whey permeate, which contains unrecoverable lactose and protein, and the minerals and vitamins originally present in the whey permeate. This byproduct is difficult to handle, and is typically land-spread (which leads to runoff, resulting in serious pollution problems in lakes and rivers), landfilled or sold for cattle feed at a loss to the factory.
There has been a growing demand in the food and pharmaceutical industries for functional and nutritionally sound mineral sources to replace the traditional sources, which often provide minerals which are impure and not easily absorbed. Minerals serve a wide variety of essential physiological functions ranging from structural components of body tissues to essential components of many enzymes and other biological important molecules.
Minerals are classified as micronutrients or trace elements on the basis of the amount present in the body. The seven micronutrients (calcium, potassium, sodium, magnesium, phosphorus, sulphur and chloride) are present in the body in quantities of more than five grams. Trace elements, which include boron, copper, iron, manganese, selenium, and zinc are found in the body in quantities less than five grams.
The natural milk minerals, particularly calcium and phosphorus, are of tremendous importance in nutrition. These minerals are essential for proper teeth and bone formation, and skeletal structure development. Calcium is the mineral element believed to be most deficient in meals in the United States. Calcium intakes in excess of 300 mg per day are difficult to achieve in the absence of milk and dairy products in the diet. This is far below the recommended dietary allowance (RDA) for calcium (1000 mg per day for adults and children ages one to ten, 1200 mg per day for adolescents and pregnant and lactating women, which equates to about four glasses of milk per day).
In fact, it has been reported that the mean daily calcium intake for females over age 12 does not exceed 85 percent of the RDA. In addition, during the years of peak bone mass development (18 to 30), more than 66 percent of all U.S. women fail to consume the recommended amounts of calcium on any given day. After age 35, this percentage increases to over 75 percent.
Although the general public is not fully aware of the consequences of inadequate mineral intake over prolonged periods of time, there is considerable scientific evidence that low calcium intake is one of several contributing factors leading to osteoporosis. In addition, the dietary ratio of calcium to phosphorous (Ca:P) relates directly to bone health. A Ca to P ratio of 1:1 to 2:1 is recommended to enhance bone marrowization in humans. Such ratios are difficult to achieve absent an adequate dietary supply of milk and dairy products, or an adequate supply of calcium and other minerals for the lactose-intolerant segment of the population.
Presently, most calcium supplements are produced from mining, from bone meal, or from oyster shells. These sources of calcium contain impurities such as lead and arsenic. High levels of such impurities could be toxic to the human system. By contrast, such impurities are filtered out naturally by the bodies of milk-producing animals such as the cow, goat, or buffalo, so that milk secreted by such animals contains only a balanced and pure form of the milk minerals, including calcium, phosphorus, potassium, magnesium, iron, and other trace elements as essential nutrients.
There have been relatively few attempts in the past to extract minerals from milk and whey. J. N. DeWitt et al reported (in Soc. Dairy Tech., 30, 112 (1978)) that demineralization of whey using ion exchange resins, after adjustment of the whey pH to 4-6, resulted in formation of a precipitate containing 90 percent lipids, 99 percent bacteria, and 10 percent of the proteins originally present in the whey. U.S. Pat. No. 3,560,219 to Attberry reported that addition of 0.075 molal concentration of calcium ion to cheese whey at a pH above 6.0 and at 60.degree. C. resulted in formation of a precipitate containing 19 percent protein, 38 percent ash, 24 percent lactose and 4.5 percent lipids on a dry weight basis. All the original fat in the whey was removed in the precipitate.
U.S. Pat. No. 5,185,166 to Nakagawa, et al., describes a process for the production of milk mineral concentrate and drink containing minerals. According to the Nakagawa process, the pH of whey is adjusted to 4 to 6, after which the whey is ultra-filtered through a membrane having a cutoff molecular weight of 40,000. The filtrate is then concentrated until the concentration of lactose reaches approximately 50 percent. The concentrate is allowed to stand for 10 to 12 hours at 0.degree. to 20.degree. C., after which time the concentrate is centrifuged to yield a milk mineral concentrate containing 25 to 35 percent ash. The Nakagawa concentrate contained only small amounts of milk minerals, for example, about 2-10% potassium, and about 2-5% calcium.
U.S. Pat. No. 4,400,315 to Thomas discloses a method to remove phosphates from deproteinized cheese whey to improve the handling characteristics of deproteinized whey used to produce lactose or hydrolyzed syrup. According to the Thomas method, the pH of deproteinized whey is adjusted to 6.4 to 7.0 (preferably 6.5 to 6.7) by adding calcium hydroxide or potassium hydroxide. The deproteinized whey is then heated to a temperature in the range of 150.degree. to 180.degree. F. and held at that temperature for about 4 hours. After the four hour holding period, calcium hydroxide is added to the heated deproteinized whey in an amount not to exceed 0.01% by weight based on the dry matter solids of the deproteinized whey. Calcium phosphates were precipitated from the deproteinized whey after the deproteinized whey was held for at least two hours to allow the mixture to cool down. The calcium phosphates undoubtedly contained minerals of unknown analysis, but were discarded as waste.
Whey permeate and delactosed whey permeate are an excellent source of natural milk minerals. It is clearly desirable to develop a process to extract milk minerals from whey products such as whey permeate and delactosed permeate, to provide a natural and readily absorbable source of such minerals, which heretofore have been discarded as wastes.